JP2004165590A - Horizontal current shielding light emitting diode led and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a horizontal current shielding LED characterized to carry out the etching of a trench to be used for shielding horizontal currents simultaneously with a process to expose a semiconductor layer with first polarity, and to prevent manufacturing costs from being increased and its manufacturing method. <P>SOLUTION: This horizontal current shielding LED is provided with a substrate 110, a semiconductor layer 130 with first polarity arranged on the substrate 100 and an active layer 150 and at least one trench 180 arranged on one portion of the semiconductor layer 130 with first polarity. This horizontal current shielding LED is also provided with a semiconductor epitaxial structure in which the depth of the trench 180 reaches at least the active layer 150, a metallic electrode pad 190 with first polarity arranged on the other portion of the semiconductor layer 130 with first polarity and a metallic electrode pad 200b with second polarity arranged on the semiconductor epitaxial structure so that the metallic electrode pad 190 with first polarity and the metallic electrode pad 200b with second polarity can be arranged at the opposite sides of at least one trench 180. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a structure of a light emitting diode (LED) and a method of manufacturing the same, and more particularly, to a structure of a lateral current blocking LED and a method of manufacturing the same.
[0002]
[Prior art]
In recent years, great attention has been focused on light emitting devices using gallium nitride type semiconductors such as GaN, AlGaN, InGaN, and AlInGaN. Typically, most of the above types of light emitting devices are grown on electrically insulated sapphire substrates and are different from other light emitting devices that utilize conductive substrates. Since the sapphire substrate is an insulator, the electrodes cannot be formed directly on the substrate, but directly contact the P-type and N-type semiconductor layers individually to complete the manufacture of the light-emitting device formed on the sapphire substrate. There must be.
[0003]
Please refer to FIG. 1 (A) showing a cross-sectional view taken along line aa ′ in FIG. 1 (B) and FIG. 1 (B) showing a top view of a conventional nitride LED. The structure shown in FIG. 1 can be formed through the following steps. First, the buffer layer 20 is epitaxially grown on the substrate 10, and the material of the substrate 10 is, for example, sapphire, and the material of the buffer layer 20 is, for example, AlN or GaN. Then first polarity semiconductor layer 30 (e.g., _{(Al x Ga l-x)} y In l-y N (0 ≦ x ≦ 1; is made of a material 0 ≦ y ≦ 1)), the first the polarity of the cladding layer 40; (for example _{(Al x Ga l-x)} y in l-y N (0 ≦ x ≦ 1 is made of a material 0 ≦ y ≦ 1)), heterostructure or a quantum well to double _{a, (Al x Ga l-x} ) y in l-y N (0 ≦ x ≦ 1; 0 ≦ y ≦ 1) active layer 50 including the second polarity of the cladding layer 60 (e.g., _(Al x Ga _l−x ) _y In _1−y N (0 ≦ x ≦ 1; 0 ≦ y ≦ 1), and a highly doped contact layer 70 of the second polarity (eg, (Al _x Gal _{− x} ) _y In _1-y N (made of a material of 0 ≦ x ≦ 1; 0 ≦ y ≦ 1) continues to be epitaxially formed on the buffer layer 20. Lengthened.
[0004]
Thereafter, the epitaxial layer is etched or polished by dry etching, wet etching, or mechanical cutting and polishing, thereby exposing a part of the semiconductor layer 30 of the first polarity. Next, a first polarity metal electrode pad 90 is attached to the exposed portion of the first polarity semiconductor layer 30 by thermal evaporation, electron beam evaporation, sputtering, or the like, and the second polarity transparent electrode 100a and the second polarity A polar metal electrode layer 100b is subsequently applied over the second polar contact layer 70.
[0005]
Although the second polarity transparent electrode 100a having the above structure can improve the current spreading effect, in fact, most of the current flows between the second polarity transparent electrode 100a and the first polarity metal electrode pad 90. The current does not flow through most of the active layer 50 due to the current flowing along the line between the transparent electrodes 100a having almost the second polarity and the metal having the first polarity. Concentrating between the electrode layer 90) and the lifetime of the LED is reduced (due to the over-concentrated current that causes the local area to become too hot). Although the current spreading effect can be improved by increasing the thickness of the transparent electrode 100a of the second polarity, the transparency of the transparent electrode 100a of the second polarity is reduced as a result.
[0006]
Furthermore, if the photons generated by the active layer 50 are emitted at a large angle to the surface of the LED, total internal reflection losses readily occur, and therefore only those photons emitted at a large angle from near the sides of the LED are more easily illuminated by the LED. Radiated out of the
[0007]
Accordingly, there are many related patents relating to the above prior art. For example, Toshiba has been working on a regrowth method that confines current (US Pat. Nos. 6,059,009 and 6,087,037), where an insulating layer is applied to the semiconductor element to achieve the effect of vertically confining current. However, the above steps are complex and therefore increase costs. LumiLed used p-metal electrode etching to improve current distribution and luminous efficiency, thereby achieving high luminous efficiency (Patent Documents 3, 4, and 5). However, the etching depth is not sufficient, so that the current path is not reliably ensured. Boston University in the United States has announced that photonic crystals can be applied to LEDs (Patent Document 6), but the drawback is that the etching depth is too deep to manufacture.
[0008]
[Patent Document 1]
US Patent No. 5,732,098 [Patent Document 2]
US Patent No. 6,229,893 [Patent Document 3]
US Patent No. 6,291,839 [Patent Document 4]
US Patent No. 6,287,947 [Patent Document 5]
US Patent No. 6,258,618 [Patent Document 6]
US Patent No. 5,955,749
[Problems to be solved by the invention]
As mentioned above, there are disadvantages associated with conventional nitride LEDs.
Therefore, an object of the present invention is that the etching of the trench used to block the lateral current can be performed simultaneously with the step of exposing the semiconductor layer of the first polarity (to make the metal electrode pad of the first polarity), Accordingly, it is an object of the present invention to provide a lateral current cutoff LED and a method of manufacturing the same, characterized in that the manufacturing cost does not increase.
[0010]
Another object of the present invention is to provide a lateral current blocking LED, wherein a trench is disposed between two metal electrodes in order to increase the possibility of current passing through an active layer (light emitting region) and the brightness of the LED. And a method of manufacturing the same.
[0011]
Yet another object of the present invention is a lateral current blocking LED and a method of manufacturing the same, wherein the trench is used to provide an opportunity for photons to be emitted from the side of the trench, and in particular, was originally totally internally reflected. A photon is generated from an active region in the central region of the element, which emits some photons through the trench from the sides of the trench, thereby increasing the output efficiency of the photons generated from the active layer. An object of the present invention is to provide a current interruption LED and a manufacturing method thereof.
[0012]
[Means for Solving the Problems]
According to the above object of the present invention, the present invention comprises a substrate, a first polarity semiconductor layer disposed on the substrate, and an active layer disposed on a portion of the first polarity semiconductor layer. A semiconductor epitaxial structure comprising a layer, at least one trench, wherein the depth of the at least one trench reaches at least the active layer, and a first epitaxial layer disposed on another portion of the semiconductor layer of the first polarity. A metal electrode pad of a polarity and a metal electrode pad of a second polarity, wherein the metal electrode pad of the first polarity and the metal electrode pad of the second polarity are disposed on the semiconductor epitaxial structure and have at least one trench. And a metal electrode pad of a second polarity such that they are disposed on opposite sides of the lateral current interruption LED.
[0013]
According to the above object of the present invention, the present invention further provides a method for manufacturing a lateral current interruption LED, which includes the following steps. That is, first, a substrate is provided, then a semiconductor layer of a first polarity is formed on the substrate, then a semiconductor epitaxial structure is formed on the semiconductor layer of the first polarity, and then a first layer of the semiconductor epitaxial structure is formed. Removing a portion of the semiconductor layer of the first polarity, thereby exposing a portion of the semiconductor layer of the first polarity, and then removing a second portion of the semiconductor epitaxial structure, thereby forming at least one trench in the semiconductor epitaxial structure. In this case, the semiconductor epitaxial structure includes an active layer, and the depth of at least one trench reaches at least the active layer, and thereafter, a first polarity metal electrode pad and a second polarity metal electrode pad are respectively formed. A first polarity metal electrode pad and a second polarity gold are formed on the exposed portion of the first polarity semiconductor layer and on the third portion of the semiconductor epitaxial structure. Electrode pads are disposed on opposite sides of the at least one trench.
[0014]
BRIEF DESCRIPTION OF THE DRAWINGS The foregoing aspects of the invention and many of the attendant advantages will be more readily appreciated by reference to the following detailed description when taken in conjunction with the accompanying drawings.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
Since the conventional structure of III-nitride LED has many drawbacks, the present invention provides a simple manufacturing method of nitride LED, thereby overcoming the drawbacks resulting from the conventional structure. However, the scope of application of the present invention includes LEDs where the positive and negative electrodes are located on the same side of the substrate, and is not limited to nitride LEDs.
[0016]
FIG. 2 shows a nitride LED according to one embodiment of the present invention. FIG. 2A is a cross-sectional view taken along line bb ′ in FIG. The structure shown in FIGS. 2A and 2B can be formed through the following steps. First, a low temperature buffer layer 120 is epitaxially grown on a substrate 110, in which case the material of the substrate 110 is, for example, sapphire, and the material of the buffer layer 120 is, for example, AlN or GaN. Then first polarity semiconductor layer 130 (e.g., _{(Al x Ga l-x)} y In l-y N (0 ≦ x ≦ 1; is made of a material 0 ≦ y ≦ 1)), the first Polar cladding layer 140 (eg, made of a material of (Al _x Gal _x ) _y In _{1 -y} N (0 ≦ x ≦ 1; 0 ≦ y ≦ 1), double heterostructure or quantum well And an active layer 150 including (Al _x Gal _x ) _y In _{1 -y} N (0 ≦ x ≦ 1; 0 ≦ y ≦ 1), a second polarity cladding layer 160 (for example, (Al _x Ga _1-x ) _y In _1-y N (0 ≦ x ≦ 1; 0 ≦ y ≦ 1), and a highly doped contact layer 170 of the second polarity (eg, (Al _x Gal _{1)). −x} ) _y In _1−y N (made of a material of 0 ≦ x ≦ 1; 0 ≦ y ≦ 1) continues on the buffer layer 120 Be grown kishal. The first polarity is positive or negative, and the second polarity is different from the first polarity.
[0017]
After the above-mentioned epitaxial structure is completed, the epitaxial structure is etched or polished by dry etching, wet etching, or mechanical cutting and polishing, thereby exposing a part of the semiconductor layer 130 of the first polarity and forming two electrodes. Between them (ie, below the second polarity contact layer 170), where the trench 180 blocks lateral current, thereby increasing the likelihood of current passing through the active layer 150. , And thus to increase the brightness. The trench 180 can be formed simultaneously with the process of exposing the first polarity semiconductor layer 130 by dry etching or wet etching (to form the first polarity metal electrode pad 190), thereby not increasing the production cost. Alternatively, trench 180 can also be formed by laser, water jet, mechanical drill, or the like.
[0018]
The depth of the trench 180 reaches at least the active layer 150, and the number of the trenches 180 is one or more. Further, at least one trench 180 can be arranged in an individual arrangement, an adjacent arrangement, or a staggered arrangement. Further, as shown in the top view of FIG. 2B, the shape of the trench 180 is not limited thereto, and may be a circle, a rectangle, an ellipse, or the like. In addition, the insulating dielectric material is further filled into the trench 180, thereby reducing short circuit events. In addition, the trench 180 is used to provide an opportunity for photons to be emitted from the sides of the trench 180, in which case, in particular, some photons that are originally totally internally reflected may pass through the trench 180 through the sides of the trench 180. Photons are generated from the active layer 150 that emits light from the active layer.
[0019]
Thereafter, a first polarity metal electrode pad 190 is attached on the exposed portion of the first polarity semiconductor layer 130 by thermal evaporation, electron beam evaporation, sputtering, or the like, and the second polarity transparent electrode 200a is formed. Then, the second polarity metal electrode pad 200b is continuously attached on the second polarity contact layer 170.
[0020]
Please refer to FIGS. 3A and 3B. FIG. 3A is a top view of the epitaxial structure of the conventional InGaN LED after the electrodes are formed, and FIG. 3B is a view after the trench 180 is etched according to the present embodiment. It is a top view of the epitaxial structure shown to A). Under the condition that the current is 20 mA and the forward voltage _Vf is 3.5 V, the relative intensity of the optical output is increased from the original 20.3 to 21.52 (6.0% increase).
[0021]
Please refer to FIGS. 4A and 4B. FIG. 4A is a top view of another conventional InGaN LED epitaxial structure after the electrodes are formed, and FIG. 4B is a view after the trench 180 is etched according to the present embodiment. FIG. 4B is a top view of the epitaxial structure shown in FIG. Under the condition that the current is 20 mA and the forward voltage _Vf is 3.5 V, the relative intensity of the optical output is increased from the original 24.0 to 24.4 (1.7% increase).
[0022]
Please refer to FIGS. 5A and 5B. FIG. 5A is a top view of another conventional InGaN LED epitaxial structure after the electrodes are formed, and FIG. 5B is a view after the trench 180 is etched according to the present embodiment. FIG. 6 is a top view of the epitaxial structure shown in FIG. Under the conditions of a current of 20 mA and a forward voltage _Vf of 3.5 V, the relative intensity of the optical output is increased from the original 24.5 to 25.5 (4.1% increase).
[0023]
In summary, an advantage of the present invention is that the etching of the trench used to block the lateral current exposes the semiconductor layer of the first polarity (to make the metal electrode pad of the first polarity) at the same time. It is an object of the present invention to provide a lateral current interruption LED and a method for manufacturing the same, which can be performed and thereby does not increase the production cost.
[0024]
Another advantage of the present invention is that a lateral current blocking LED in which a trench is disposed between two metal electrodes, thereby increasing the likelihood of current passing through the active layer (light emitting region) and increasing the brightness of the LED And a method for producing the same.
[0025]
Yet another advantage of the present invention is that the trench is used to provide an opportunity for photons to be emitted from the sides of the trench, wherein the photons originate from an active region in the central region of the element. An object of the present invention is to provide a lateral current interruption LED and a method of manufacturing the same. In particular, some photons that are originally totally reflected can be emitted through the trench from the sides of the trench, thereby increasing the output efficiency of the photons arising from the active layer.
[0026]
It will be appreciated by those skilled in the art that the above preferred embodiments of the present invention are illustrative of the present invention rather than limiting of the present invention. It is intended to cover various modifications and similar arrangements, which fall within the spirit and scope of the appended claims, the scope of which is to cover such modifications and similar structures. Should be given the broadest interpretation.
[Brief description of the drawings]
FIG. 1A is a cross-sectional view taken along a line aa ′, and FIG. 1B is a top view showing a conventional nitride LED.
FIGS. 2A and 2B are diagrams illustrating a lateral current blocking nitride LED according to an embodiment of the present invention, wherein FIG. 2A is a cross-sectional view taken along line bb ′ in FIG. Is a top view.
FIG. 3A is a top view showing an epitaxial structure of a conventional InGaN LED after electrodes are formed, and FIG. 3B is a top view showing an epitaxial structure after a trench etching step according to one embodiment of the present invention. FIG.
FIG. 4A is a top view showing another conventional InGaN LED epitaxial structure after an electrode is formed, and FIG. 4B is a view after a trench etching process according to an embodiment of the present invention is performed. 3 is a top view showing the epitaxial structure of FIG.
FIG. 5A is a top view illustrating an epitaxial structure of still another conventional InGaN LED after electrodes are formed, and FIG. 5B is a diagram illustrating a trench etching process according to an embodiment of the present invention. It is a top view which shows the epitaxial structure after.
[Explanation of symbols]
110 substrate 120 buffer layer 130 first polarity semiconductor layer 140 first polarity cladding layer 150 active layer 160 second polarity cladding layer 170 second polarity highly doped contact layer 180 trench 190 first polarity Metal electrode pad 200a Transparent electrode 200b of second polarity Metal electrode pad of second polarity

Claims (2)

A lateral current blocking light emitting diode,
Board and
A first polarity semiconductor layer disposed on the substrate;
A semiconductor epitaxial structure having an active layer and at least one trench disposed over a portion of the first polarity semiconductor layer, wherein the depth of the at least one trench reaches at least the active layer An epitaxial structure;
A first polarity metal electrode pad disposed on another portion of the first polarity semiconductor layer;
A second polarity metal electrode pad disposed on the semiconductor epitaxial structure, wherein the first polarity metal electrode pad and the second polarity metal electrode pad are disposed on opposite sides of at least one trench. A second polarity metal electrode pad,
A transverse current blocking light emitting diode comprising: A method of manufacturing a lateral current cutoff LED,
Providing a substrate;
Forming a semiconductor layer of a first polarity on a substrate;
Forming a semiconductor epitaxial structure on the semiconductor layer of the first polarity;
Removing a first portion of the semiconductor epitaxial structure, thereby exposing a portion of the first polarity semiconductor layer;
Removing a second portion of the semiconductor epitaxial structure, thereby forming at least one trench in the semiconductor epitaxial structure, wherein the semiconductor epitaxial structure has an active layer and the depth of the at least one trench is at least active. Steps to reach layers,
Forming a first polarity metal electrode pad and a second polarity metal electrode pad on the exposed portion of the first polarity semiconductor layer and on the third portion of the semiconductor epitaxial structure, respectively; A first polarity metal electrode pad and a second polarity metal electrode pad are disposed on opposite sides of at least one trench;
A method for manufacturing a lateral current blocking light emitting diode, comprising:

Images